1. Field
Embodiments relate to a mask assembly, a deposition apparatus for flat panel displays including the same, and associated methods.
2. Description of the Related Art
Flat panel displays may exhibit desirable characteristics, e.g., light weight, low thickness, and so on. Typical examples thereof may include, e.g., liquid crystal displays (LCDs) and organic light emitting diode displays (OLEDs). Among them, OLEDs may be implemented as ultra thin displays because of their excellent brightness, wide viewing angle, and absence of a backlight, as compared to LCDs.
An OLED is a display device in which electrons injected from a cathode and holes injected from an anode are recombined to form excitons in an organic thin film. Radiation having a specific wavelength may then be emitted by a release of energy resulting from de-excitation of the excitons.
In the OLED, e.g., photolithography or deposition using a mask assembly having a plurality of slits formed in a predetermined pattern, may be used to selectively form a negative electrode, a positive electrode, and an organic thin film on a substrate. The substrate may be formed of, e.g., glass, stainless steel, or synthetic resin. Because moisture may be introduced during a step of stripping photoresist using wet or dry etching during a photolithography process, deposition using the mask assembly should be used when depositing materials that may be degraded by moisture, e.g., organic thin films.
An OLED may include an organic light emitting element having red (R), green (G), and blue (B) organic light emitting layers in order to display a full range of colors. Deposition using the mask assembly may deposit a thin film having a pattern corresponding to the predetermined pattern. Deposition may occur on a substrate by aligning the mask assembly between the substrate and an evaporation source and then allowing a deposition target to be deposited on the substrate through the mask assembly. Thus, to fabricate the full-color OLED, the mask assembly may include a pattern mask having the predetermined pattern thereon and a frame mask supporting the pattern mask.
The mask assembly may be fabricated by an etching method including, e.g., forming slits by an etching process or an electroforming method using electrolysis. The etching method may be limited in its ability to form the slits in a highly precise pattern because a width of the slit and an interval therebetween may be limited by a thickness of a material. On the other hand, the electroforming method may be used to fabricate the slits with relatively high precision compared to the etching method.